This invention relates generally to roll baling machines typically referred to as round balers which form cylindrical roll bales of crop material. In particular, this invention relates to a breakaway mechanism for a twine wrapping apparatus on such roll baling machines.
U.S. Pat. No. 4,062,279 discloses a breakaway mechanism including a first lever fixed at one end to a sleeve which in turn is secured to a rotatable shaft carrying a twine tube. A second lever is coupled to the other end of the first lever opposite the sleeve by a coupling device in the form of a ball that is spring loaded against the first lever. A hub, fixed to the second lever, receives the sleeve fixed to the first lever. The second lever is connected to a hydraulic cylinder for effecting pivoting movement of the twine tube. If the twine tube encounters an obstruction during its pivoting movement that is sufficient to overcome the spring loading on the ball of the coupling device, the first lever breaks away from the second lever and the twine tube remains stationary while the second lever and the hub rotate about the sleeve fixed to the first lever. A disadvantage of this breakaway mechanism is that it is difficult to accurately adjust the spring loading on the ball. Another disadvantage of this breakaway mechanism is that it is rather large and thus occupies an excessive amount of space.